Wheel balancer



April 2, 1940.

H. c. SCHILDMEIER WHEEL BALANCER INVENTOR. flf/mr 6. Swap/15am BY W ATTORNEYS.

1 a m a .v 7 a m5 2 n E E 1 Z 8 7 3 9 l v v. J r lllll 4 d e l 1 L P 2, 1940- H. c. SCHILDMEIER WHEEL BALANCER Filed July 26, 1957 2 s-$11881. 2

r ATTORNEY5.

Patented Apr. 2, 1940 UNITED STATES PATENT OFFICE 7 Claims.

This invention relates to a balancing machine which is particularly useful in balancing wheels and brake drums of automobiles but is equally useful for the balancing of rotating parts of other types of machinery.

In the balancing of a rotating element, it is usualpractice to add weights to the element in the proper amount and proper position to counter-balance such excessive weight as there may be in other parts of the element. It is necessary, therefore, that an eflicient balancing machine should promptly indicate both the amount and position of the weight to be added. The principal object of the present invention is to provide a balancing machine which gives this necessary information with a high degree of ac curacy and speed.

Other objects of the invention and the manner inwhich these objects are attained will be apparent "from the following specification and claims and the accompanying drawings in which a preferred form thereof is illustrated in detail.

Fig. 1 is a perspective view of the balancing machine with an automobile wheel and tire attached thereto for balancing. Fig. 2 is an end view of the left end thereof with an enclosing. casing removed to show the interior construction in detail. Fig. 3 is a front view with the casing removed and with parts cut away. Fig. 4 is a similar view on a large scale of a portion of the right end of the machine with parts removed. Fig. 5 is a fragmentary sectional view taken substantially on the line 5-5 of Fig. 3. Fig. 6 is a fragmentary plan view of a portion of the machine. Fig. 'I is a second fragmentary plan view of another portion of the machine. Fig. 8 is a diagram of wiring connections used for certain electrical parts thereof. I

In the form of the invention shown in the drawings by way of illustration, the stationary frame of the machine consists of a deck plate l6 supported by four vertical legs positioned on the four comers thereof. The lower portion of the machine is enclosed by a removable housing l2, and the upper portion by a second removable housing l3. In the drawings, with the exception of Fig. 1, the housings l2 and I3 are removed to show other parts in detail.

On the upper surface of the deck plate Hi there is provided a rigid bearing bracket |4 having horizontal arms l5 and I6. Each of said arms carries an adjustable screw l1 and the ends of said screws pivotally support a-bearing 3. Said bearing rotatably supports one end of a horizontal shaft Ill. The bearing I8 is preferably of the ball type.

The opposite end of said shaft is carried by a ball bearing 26 contained within a housing 2|. The housing 2| is provided with ears 2? to which 5 there are pivotally secured, by means of pins 23, a pair of vertical supports 24- preferably formed of spring steel. The lower ends of the suports 24 are secured to the deck plate It. By means of this construction, the shaft I 9 is free to vibrate i horizontally about a pivot formed by the ends of the screws A frame member 25 supported by the deck plate l6 carries bumpers 26, preferably of soft rubber or other resilient substance, in position to engage the ears 22 and to resiliently l limit the amplitude of said vibration.

Adjacent the bearing I8 the shaft l9 carries a pulley 21 which may be driven by a belt 28 from a pulley 29 mounted upon the shaft of a motor 30. The belt 28 passes through suitable openings in the deck plate It]. The shaft of the motor, 36 carries'a second pulley 3| about which there is trained a belt 32 which also passes over a pulley 33 carried by the shaft of a motor 34. The motor 36 is mounted. upon, aplate 35 piv- 26 otally supported by means of a rod 36 and cars 31 upon a cross bar 38 extending between the rear pair of legs The opposite-end of the plate 35 is supported upon a nut 39 threadedly engaged with a vertical rod 46, the upper end of 30 which isconnected to a clutch lever. 4|. Said clutch lever is pivotally mounted upon a lug 42 secured to the under surface of the deck plate Ill. The opposite end of said lever operates in a hook shaped slot 43 in the housing I 2, best seen 85 in Fig. 1.

The motor 34 is mounted on a plate 44 pivotally mounted at oneedge by means of a rod 45 and lugs 46 on the under surface of the plate 35.

A portion of the weight of the motor 34 and plate 40.

44 is carried by the belt 32 and thus maintains the necessary tension on said belt for the motor 34 to drive the same. When the clutch lever 4| is permitted to rest in the elongated lower portion 41' of the slot 43, the weight of both motors 45 and both plates 35 and 44 is carried in part by the belt 28 and thus maintains the proper tension "in said belt to permit either of'said motors to rotate the shaft l9. When the lever 4| is manually moved upward and placed in the shorter upper portion of the slot 43, the tension on the belt 23 is relaxed to the point. where the shaft It will not be rotated. One of the motors is adapted to drive the shaft at a higher speed than the other, the motor 30 u preferably being the high speed motor and the motor 34 being the low speed motor.' If desired, one of said motors may be of a variable speed type to provide a greater range of speed for the shaft I9. Ordinarily, however, it is only necessary to have one low speed for the balancing operation and one higher speed for checkingthe balance when the operation is complete. Power for said motors is controlled by means of snap switches 48 and 58 carried by the housing I3. standard type and need not be shown in detail.

Adjacent the pulley 21 the shaft i8 carries a brake drum 5| about which there is trained a brake band 52. extends through a suitable opening in the deck plate I0 and is anchored at 53 to a lug 54 formed on the lower surface of the deck plate Ill. The opposite end of said brake band is anchored at 55 to a brake lever 56 which is pivotally mounted to the lug 54 andextends outwardly through a suitable opening in the casing I2. The weight of the lever 58 is insufiicient' to apply an' appreciable braking pressure to the drum 5|. However, a manual downward pressure on the lever 58 provides suflicient braking pressure to bring the shaft I9 to a rapid stop when the power has been cut from the motors 30 and 34 or the Outside of the bearing- 2II-the shaft I8 carries a face plate 51 keyed thereto. Said face plate has a central recess 58 and may be p ovided with suitable recesses in the face thereof to receive such projections as there may be on the elements to be'balanced by the machine. A

cone 58 is slidably mounted on the shaft I8 and when moved'close to the face plate 51 en ages a s line 80 mating with a keyway 6| therein -which adeuuatelv prevents rotation of the cone.

In mountin the wheel 82 or other eement to be balanced. the cone is removed. the wh el placed in position a ainst the face plate 51 and the cone is then repla ed and enga es the central hole in the w eel. The whole structure is locked in place hv a nut 83 which thread dlv en a es the sha t I8 and ma h turned against the outer Su face of the cone 58.

To t left of the bearin homing 2| the shaft I8 carries a cylind i al drum 64. the outer surface of which is nreferaby formed of insulating ma erial. For this purpose. a wood or. paper faced pullev may be u ed. An electric conduc or G5 is inset in a helical roove formed in the outer surface of the drum 64 and is electrically conn cted by a wi e 8 with a metallic portion of the drum 84 which is in electrical contact w th the shaft I8. If desired. the drum mil-Y in the form of an upraised heical fin.

Ad ac nt the drum 84. an S-shaped member the d ck late In and carries on its u per face an insulation block 88 on which there is mounted parallel to the axis of the shaft 8 and the face of the drum 84. Preferably the conductor 88 is in the form of a serrated member or comb having a plurality of teeth 18 proiecting toward secured to the S-shaped spring 81 and projects through a suitable opening in the housing I8. Said knob may be pressed to move the teeth 18 closer to the drum 84 and when released permits The wiring of these motors may be of a One end of said brake band' clutch lever 4| has been operated to slacken tenv sion on the belt 28.

be enti el me al ic. t e. conductor 5 being made 81. referahlv of s rin steel. is mounted upon a conductor 88 havin its inner .edge enerally the drum 84. A rod 1| carrying a knob 12 isthe same to-be moved by the spring 81 away from said drum.

The frame member 25 has secured thereto a vertical member 13 to which is secured an E- shaped magnetic core 14. A reactance coil 15 is wound about the central stem of the core 14 and an armature 16 is hinged to said core at 11. Adjacent the'upper edge of the core 14 there are secured'a pair of leaf springs 18 secured together by a bolt 18, the effective length of which may be adjusted by a nut 88. The springs 18 engage the edges of the armature 16 and frictionally retain the same in any position in which it may be placed by other means. An extension 8| is secured to the armature 15 and is arranged in the path of travel of a stem 82 adjustably secured by means of nuts to a lug 84 formed on the bearing housing 2|. By this means the horizontal vibrations of the shaft I9 are'transmitted to the 'stem 82. The stem 82 striking the extension 8| moves the same and the armature 16 outwardly a distance proportional to the amplitude of the vibrations. The armature is retained in this position by means of the springs 18 until it is manually reset by means of a lever 85. Said lever is pivotally mounted at 86 on the upper end of a bracket 81 supported on the deck plate I8. One end thereof is in position to engage the armature 16 to press the same into an initial position against the core 14 and the opposite end of said'lever extends through a suitable opening in the housing I8 on the side not visible in Fig. 1. A tension spring 88 normally retains the lever 85 against a stop pin 88 out of engagement with the armature 18.

' In Fig. 8 there is shown a diagram of a preferred form of electrical connection in which power is supplied on a pair of power mains 88 in one of which there is indicated a snap switch 8|. The power mains 88 may be connected to any suitable source of alternating current, preferably 110- volt, cycle. -The mains are a shunt 88 to which there is connected 9. milliammeter 88.

The transformer 82 delivers alternating current at a voltage to suit the characteristics of the coils 15, rectifier 8 8 and the miiliammeter 88.

when switch 8| .is closed. current is drawn from the transformer secondary through the circuit 82, 88, 18, 84, 85, 88, 82 and the amount of said current. depends upon the inductance of the coil 18 which in turn depends upon the position of the armature 18 with relation to the core 14. The amountof this current is indicated .by the milliammete'. 88.

-There is also connected to the secondary windings of transformer 82, by means of conductors I88 and III, a high tension induction coil I82, preferably of the vibrating make-andbreak type. Induction coil I82 has one of its secondary terminals grounded at I88 on the frame of the machine. Since theconductor is grounded through the metallic portion of drum meet an electric connection between said conductor and said sec-" 00 and shaft I9, there is in ondary terminal. The opposite secondary terminal of coil I02 is connected by a conductor I04 to the comb 69. By this wiring there is formed a high tension circuit (I02, I04, 09, 60, I9, I 03, I02) which has an air gap between the comb 69 and the conductor 89. The voltage delivered by the coil I02 is sufiicient to cause a spark to jump between the conductor 09 and the nearest of the teeth I0. In the rotation of the drum 04 sparks are successively discharged between each of said teeth and the conductor 05.

. At any given instant the position of the spark 15' discharge on the comb 69 indicates the instantaneous angular position oi the shaft in its rotation. When said drum is rapidly rotated, sparks are discharged in such rapid succession as to give the impression of a row of continuous discharges which are visible through an opening I05 in the housing I3.

Inthe operation of the apparatus, a wheel 62 or other element to be balanced is secured to the shaft I9. Armature I6 is set in its initial position against core I4 by means of lever 85. The switch 9| is closed and the low'speed motor 34 is started. The clutch lever 4| is then operated to start rotation of the shaft I9 and the wheel carried thereby. If the wheel is out of balance, the shaft I9 vibrates horizontally about the ends of the bolts I1 and the amplitude of this vibration is a measure of the weight which must be added to balance the wheel. The vibration is transmitted to the stem 82 which strikes the armature extension 8| and thus places the armature 16. in a position corresponding to the said amplitude. The current flowing through the coil I5 is affected by the position of the armature and this eifect is indicated by the milliammeter 99. For a given diameter of wheel, the amplitude of vibration is a direct measure of the amount of weight which must be added at the rim of the wheel to balance the same. Therefore, the scale of the milliammeter may be constructed to read directly the amount of weight to be added for a wheel of a certain size. The meter, of course, may carry several scales calibrated for several sizes of wheels. 'On each of these scales, the point marked Zero will correspond to the current flowing through the meter when the armature I6 has been placed in its initial position resting against the core II.

' on the wheel. The conductor 65 draws ashorter As the shaft I9 rotates with an unbalanced wheel secured thereto, the horizontal vibrations have the same frequency as the rotation. For that reason, one particular point on the periphery of drum 64 approaches closer to the comb 89 at each revolution than any other point of said drum. The location of this point is determined by the position of the unbalanced weight spark from the tooth of the comb corresponding to this particular point than from any other tooth. Since the rotation 01' the drum is sumciently fast for each of the sparks to appear asa continuous discharge, it is easy to compare the lengths of the several sparks and to deter-v mine which is the shortest. when once the shortest spark has been located, the machine is stopped and the shaft and wheel are rotated by hand until a spark appears at the previously determined pointon the comb 09 at which the.

shortest spark appeared. The necessary weight as indicated by the milliammeter is then added to the rim of the wheel opposite an index mark shaft I9 to the desired I00 on the housing IS. The position of the index mark is determined empirically. It has been found in practice that the position 01' the added weight varies with the amount of weight to be added for a given size of wheel and also varies with diflerent types and-sizes of elements to be balanced. However, when once determined. the position of the index mark holds good for a similar set of conditions. A plurality of such indices suitably labeled are, therefore, provided for varying sizes and typesv of elements to be balanced and for various amounts of weight to be added.

When the proper amount of weight has been added at the position of the index mark, the low speed motor is stopped and the high speed motor 30 is started to check the final balance. Obviously, the amplitude of vibration for a given amount or unbalance at high speed would be greater than at a low speed but it has been found in practice that in the great majority of cases the high speed check shows practically no vibration when the weight has been added as indicated by the low speed test. I1, however, the high speed check shows an appreciable unbalance, .the low speed test is repeated to secure a finer adiustment of balance. A tachometer I01 may be mounted on the housing I3 and suitably connected to the shaft I9 to indicatethe speed of rotation of the shaft I9. By this means, the high speed checkmay be made at the actual speed at which the element under test is to operate. When a variable speed motor is not used in this check, it-is only necessary to 'run the high speed motor long enough to bring the operating speed, even lower than the maxi- The original low speed balancing operation must, of

course, be carried out at a predetermined fixed speed.

From the foregoing specification, it will be obvious that the machine provides for the rapid determination of both the amount and position of the weight to be added after the wheel has been placed in position. The determination of ths information need require but a few seconds. Since the mounting of the object and its removal are very simple, a large number may be balanced in an extremely short time.

The foregoing specification describes a preferred form oi the invention the details of which may be varied between widelimits without departing from the scope of the invention as defined in the appended claims. For example, the comb 69 may be formed with a straight edge rather than a serrated edge. In that case, the spark discharge appears as a narrow band giving the appearance of a continuous sheet whichhas its narrowest point adjacent the portion of concharge of greater intensity with less voltage. An-

other example of a possible variation is that the supports 24 maybe suspended from an-overhead bridge with bearing housing ZI carried by the lower ends thereof; Thisis a mere reversal of parts which is preferable for balancing objects of greater weight than can be accommodated when the springs fl act-as columns to carry the weight.

The invention claimed is: 1. In a balancing machine, the combination of a rotatable shaft, on which an element to be balanced may be mounted, means for rotating said shaft, 9, bearing for said shaft adjacent each end, at least one of said bearings being mounted to permit vibration of said shaft in a direction transverse thereto, a helical electric conductor mounted on said shaft coaxial therewith and rotatable therewith, a relatively stationary serrated conducting member mounted with the line of the teeth thereof substantially parallel to the axis of said shaft and spaced from the path of travel of said helical conductor, and means for producing an electric spark discharge between adjacent portions of said conductors.

2. In a balancing machine, the combination of a rotatable shaft, on which an element to be balanced may be mounted, means for rotating said shaft, a bearing for said shaft adjacent each end, at least one of said bearings being mounted to permit vibration of said shaft in a direction transverse thereto, a helical electric conductor mounted on said shaft coaxial therewith and rotatable therewith, a relatively stationary conductor arranged generally parallel to the axis of said shaft and spaced from the path of travel of said helical conductor, and means for producing an electric spark discharge between adjacent portions of said conductors.

3. In a balancing machine, the combination of a rotatable shaft on which an element to be balanced may be mounted, said shaft having one end resiliently mounted to permit vibration in a direction transverse to theaxis of rotation, a helical electric conductor mounted on said shaft coaxial therewith and rotatable therewith, a rel: atively stationary serrated conducting member mounted with the line of the teeth thereof substantially parallel-to the axis of said shaft and spaced from the path of travel of said helical conductor, and means for. producing an electric spark discharge between adjacent portions of said conductors.

4. In a balancing machine, the combination of a rotatable shaft on which an element to be balanced may be mounted, said shaft having one end resiliently mounted to permit vibration in a direction transverse to the axis of rotation, a helical electric conductor mounted on said shaft coaxial therewith and rotatable therewith, a relatively stationary conductor arranged generally parallel to the axis of said shaft and spaced from the'path of travel of said helical conductor, and means for producing an electric spark discharge between adjacent portions of said conductors.

5. In a balancing machine, the combination of a rotatable shaft on which an element to be balanced may be'mounted, said shaft having one end resiliently mounted to permit vibration in a direction transverse to the axis of rotation, an induction coil having a magnetic core and a movable armature, means movable by the vibration of said shaft to move said armature through a distance corresponding to the amplitude of said vibration, a normally closed alternating current electric circuit including said induction coil, the amount of current flowing in said circuit being determined by the position of said armature, and means for measuring said current flow.

6. In a balancing machine, the combination of a rotatable shaft, on which an element to be balanced may be mounted, means for rotating said shaft, a bearing for said shaft adjacent each end, at least one of said bearings being mounted to permit vibration of said shaft in a direction transverse thereto, an induction coil having a magnetic core and a movable armature, means movable by the vibration of said shaft to move said armature through a distance corresponding to the amplitude of said vibration, a normally closed alternating current electric circuit including said induction coil, the amount of current flowing in said circuit being determined by the position of said armature, and means for measuring said current flow 7. In a balancing machine, the combination of a rotatable shaft on which an element to be balanced may be mounted, said shaft having one end resiliently mounted to permit vibration in a direction transverse to the axis of rotation, an induction coil having a magnetic core and a movable armature, means movable by the vibration of said shaft to move said armature through a distance corresponding to the amplitude of said vibration, means frictionally retaining said armature in the position in which it is placed by said last mentioned means, an electric circuit supplied with alternating current and including said induction coil, and means for measuring the current flowing in said circuit.

. HENRY c. scammmaa. u 

